Membrane Processes in Water and Wastewater Treatment

Membrane Processes in Water and Wastewater Treatment

DOI: 10.4018/978-1-7998-2645-3.ch005

Abstract

Membrane technologies play a very important role in water and wastewater treatments. These membrane processes provide key advantages over the conventional processes, such as lower energy requirement, lower footprint, easier to operate, and more effective contaminants removal. This chapter introduces different membrane processes: (1) pressure-driven membrane processes which are the most widely used in water and wastewater treatments, and (2) several advanced membrane processes. These processes perform physical or physicochemical separations. Most of the separations occur between liquid-liquid phases, but liquid-gas and gas-gas separation phases are also performed in the latest membrane development. The contemporary membrane bioreactor is the heart of membrane technologies that are used in various applications. However, fouling is a common phenomenon that reduces the efficiency of the membrane operation. Thus, the concept of critical flux and introduction of some control and preventive mechanism could prevent or reduce the fouling in membrane bioreactors.
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Introduction

A Brief History Development of Membrane Technology

The early study of membrane field can be trailed back to the eighteenth century, when the term “osmosis” was first introduced by Jean-Antoine (Abbé) Nollet in 1748 which signifies the water permeation across a diaphragm. In his study, Nollet experimented using pig bladder as the membrane material. Yet through the 1800s until early 1900s sees no commercial application for membrane, except as laboratory experimentation tool to acquire breakthrough in physical and/or chemical theories in membrane field. These were the golden period to study this relatively new field which has brought to the discovery of van's Hoff equation and the development of the kinetic theory of gases using the model of the selective semipermeable membrane by Maxwell. It wasn't until two centuries later before membrane technologies have seen tremendous development and evolution in terms of their use of materials, designs, operations, as well as their applications.

In terms of membrane material, early membrane researches experimented with available diaphragms such as pig, cow, and fish bladder, and animal gut. Other materials were subsequently used to make membrane such as collodion (nitrocellulose), and other polymers like cellulose acetate which are still extensively used today. However, the membrane has yet been widely used for separation application let alone commercialized due to significant problems aroused with the available membranes. These drawbacks included membrane being very undependable, low flux, unselective and expensive. Industrial application of membrane was made possible at the beginning of 1963 through the Loeb-Sourirajan process. Loeb and Sourirajan’s work managed to produce reverse osmosis membrane characterized by fault-free, high flux, asymmetric membrane. The membrane developed was a practical method to desalt water. This innovative commercialization gave birth to the progression of other membrane types such as microfiltration and ultrafiltration.

The peak development of these membranes was in the mid-1990s to treat municipal water and integrated with the membrane bioreactor systems to treat sewage. The swift growing of wastewater treatment application using membrane technology was made possible through scaling up and commercialized installation of the system by leading companies like Mitsubishi Rayon, Kubota and Zenon. Since then, membrane technology utilization in water and wastewater application has been widespread in various countries around the world.

In Singapore for example, membrane technology has gained significant interest in wastewater treatment application. Due to land scarcity, Singapore faced a problem of water shortage as a result of the lack of natural water resources. Strategic planning, investment, and management on its water technology helped Singapore to overcome these problems mentioned beforehand. Currently, Singapore has four major water sources termed as the “Four National Taps” which are water obtained from their local collection area, imported from Malaysia, reclaimed water known as the NEWater, and desalinated water. Membrane bioreactor technology has been extensively studied for the application of water reclamation. In 2003, a pilot study on the membrane bioreactor technology was initiated at Bedok Water Reclamation Plant to analyse on the design and operation suitable to the tropical environment of Singapore. It was able to produce a good feed water quality for the production of NEWater through membrane bioreactor/reverse osmosis system. The result was very satisfactory which leads to the opening of a municipal-scale plant with a capacity of 23 million litres per day (MLD) at Ulu Pandan Water Reclamation Plant in 2006. Domestic wastewater is treated to supply clean process feed water to industries which are coined as the Industry Water. The systems are feasible because of the low economy of scale on the membrane systems. Moreover, another membrane bioreactor plant was planned to be commissioned in 2011 at Jurong Water Reclamation with a capacity of 68 MLD.

Membrane technology researches in Australia were initiated in the late 1990s. In 2002, the first full-scale operation of the membrane bioreactor system was erected at Picnic Bay on Magnetic Island, Australia. The shortage in freshwater supply forces for the water recycling initiative, which subsequently becomes the main driving force for the elevating utilization of membrane technology. The water recycling initiative is an initiative to save water resources via water reuse for not-for-drinking application. For example, reusing domestic water from sinks and showers for agriculture irrigation and toilet flushing. However, domestic sewage and industrial wastewater would need further treatment before they can safely be reused for other purposes. One of the largest applications of membrane bioreactor in Australia is the Gippsland Water Factory in Australia, commissioned in 2010. The treatment facility treated both domestic sewage and pulp and paper mill wastewater with a capacity of 35 MLD. To date, membrane bioreactor has been extensively used here from a small system at household to a large sewage treatment plant.

In Malaysia, membrane bioreactor technology has yet been implemented for treating manufacturing or municipal wastewater. The reasons are due to:

  • Lack of awareness into the insights of this promising technology by the government, policymakers, and treatment facility operators; and with the mindset that the technology is expensive and difficult to install and run;

  • High capital investment in commencing the sophisticated and advanced membrane bioreactor technology, which could be out of the financial capacity of private sectors;

  • The low economy of scale in membrane bioreactor technology compared to conventional technology in many industries, making the technology hard to be rationalized.

Nonetheless, continuous research and analysis to study the feasibility of membrane technology implementation in Malaysia provide promising insights for the future prospect. In University Malaysia Sabah (UMS), membrane technology development is comprehensively ongoing with some new technology being proposed for various applications. The Membrane Research Group in UMS was first established by Professor Ir Dr Rosalam Sarbatly in 2006, located at the School of Engineering and Information Technology (SKTM). The research evolved from membrane production to utilization in different application, particularly in wastewater treatment and seawater desalination. The membrane fabrication comprised of flat sheet membrane and hollow fibre membrane made from polymeric and ceramic based. Another invention by the research group was on the membrane distillation technology essentially for groundwater treatment. This technology is also predominantly used to cater to the needs mainly in the oil and gas industry. Presently, the research group is extensively researching on the membrane application for freshwater production through the up-flow sand filtration system coupled with microfiltration. This research is especially critical and vital to fulfilling the needs of particularly the people in rural and isolated areas who have strict access to fresh, clean water.

Key Terms in this Chapter

Dead-End Filtration: A type of membrane operation mode where feed flow is perpendicular to the membrane surface.

Transmembrane Pressure: Pressure that is required to force water through the membrane, or the pressure difference between the feed and permeate.

Critical Flux: The flux above which fouling occurs.

Membrane Technology: Collection of the separation processes which utilize membrane.

Membrane Bioreactor: A membrane technology which combines two units: a bioreactor for the biological reaction, and a membrane system for the separation process, typically either microfiltration or ultrafiltration.

Fouling: Accumulation of unwanted substances on the membrane surface or inside the membrane pores which reduces the membrane performance.

Cross-Flow Filtration: A type of membrane operation mode where feed flow is tangential (or parallel) to the membrane surface.

Reverse Osmosis: Membrane process that separates salts and tiny molecules from water using membrane at relatively high pressure, which is generally used in water desalination and purification treatment to produce clean and drinkable water.

Ultrafiltration: Membrane process of removing very small suspended particles, colloids, and dissolved materials ranging in the size of 1 – 100 nm from water using finely porous membrane filter.

Microfiltration: Membrane filtration process which separates suspended particles from water by utilizing porous membranes medium with a diameter in the range of 0.1 to 10 µm.

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